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VOLUME 15, ISSUE 2, ARTICLE 20 Ethier, D., P. Davidson, G. H. Sorenson, K. L. Barry, K. Devitt, C. B. Jardine, D. Lepage, and D. W. Bradley. 2020. Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, . Avian Conservation and Ecology 15(2):20. https:// doi.org/10.5751/ACE-01711-150220 Copyright © 2020 by the author(s). Published here under license by the Resilience Alliance.

Research Paper Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, Canada Danielle Ethier 1, Pete Davidson 1, Graham H. Sorenson 1, Karen L. Barry 2, Karen Devitt 3, Catherine B. Jardine 1, Denis Lepage 1 and David W. Bradley 1 1Birds Canada, 2Habitat Conservation Trust Foundation, 3City of Port Moody, British Columbia

ABSTRACT. Waterbirds are often used as indicators of ecosystem function across broad spatial and temporal scales. Resolving which are declining and the ecological characteristics they have in common can offer insights into ecosystem changes and their underlying mechanisms. Using 20 years of citizen science data collected by the British Columbia Coastal Waterbird Survey, we examine species-specific trends in abundance of 50 species in the Salish and 37 species along the outer Pacific Ocean coast that we considered to form the core wintering coastal community of British Columbia, Canada. Further, we explore whether ecological commonalities increase the likelihood of a species undergoing declines by testing the hypotheses that waterbird abundance trends are influenced by dietary specialization and migration distance to breeding grounds. Results suggest that most populations are stable (i.e., temporal trends are not significant) in both the Salish Sea (36 of 50 spp.) and Pacific coast (32 of 37 spp.) regions. Twelve species displayed significant decline trends in the Salish Sea, whereas two had significant increases. Along the Pacific coast, only three species displayed significant decline trends, and two significant increases. This result is corroborated by guild-specific trends indicating that waterbirds occupying the Salish Sea are faring significantly worse than those residing along the outer coastal regions, almost irrespective of dietary specialization or migration distance. Our results provide evidence that differential environmental pressures between the inner and outer coastal regions may be causing overall loss of wintering waterbirds within, or abundance shifts away from, the Salish Sea. Potential mechanisms responsible for these observed patterns are discussed, including environmental (e.g., climate) and human-induced (e.g., nutrient and chemical pollution) pressures. Collaborative, inter-disciplinary research priorities to help understand these mechanisms are suggested.

Vingt ans de suivi d'oiseaux aquatiques côtiers montrent des tendances régionales de pressions environnementales en Colombie-Britannique, Canada RÉSUMÉ. Les oiseaux aquatiques sont souvent utilisés comme indicateurs du fonctionnement des écosystèmes à de larges échelles spatiales et temporelles. La détermination des espèces en diminution et des caractéristiques écologiques qu'elles ont en commun permet de se faire une idée des changements dans les écosystèmes et des mécanismes sous-jacents. Au moyen de 20 ans de données de science citoyenne collectées lors du Coastal Waterbird Survey de la Colombie-Britannique, nous avons examiné les tendances dans l'abondance de 50 espèces dans la mer des Salish et de 37 espèces plus au large de la côte de l'océan Pacifique que nous avons considérées comme formant le noyau de la communauté d'oiseaux côtiers hivernant de la Colombie-Britannique, au Canada. En outre, nous avons étudié si les traits communs écologiques augmentaient la probabilité qu'une espèce subisse une baisse en testant les hypothèses selon lesquelles les tendances de l'abondance des oiseaux aquatiques étaient influencées par la spécialisation alimentaire et la distance de migration vers les sites de reproduction. Selon nos résultats, la plupart des populations étaient stables (c.-à-d. que les tendances temporelles n'étaient pas significatives) dans la mer des Salish (36 sur 50 sp.) et le long de la côte du Pacifique (32 sur 37 sp.). Douze espèces ont montré une tendance significative de diminution dans la mer des Salish, tandis que deux ont connu des augmentations significatives. Le long de la côte du Pacifique, seules trois espèces ont affiché une tendance à la baisse significative, et deux des augmentations significatives. Ce résultat est corroboré par les tendances propres à chaque guilde indiquant que les oiseaux aquatiques qui occupent la mer des Salish se portent nettement moins bien que ceux qui se tiennent plus au large des côtes, presque indépendamment de leur spécialisation alimentaire ou de leur distance de migration. Nos résultats montrent que les pressions environnementales variables entre les parties intérieures et extérieures des régions côtières peuvent être à l'origine de la perte globale des oiseaux aquatiques hivernant dans la mer des Salish ou d'un déplacement de ces oiseaux vers d'autres régions. Nous avons examiné les possibles mécanismes responsables des tendances observées, y compris les pressions environnementales (p. ex. le climat) et humaines (p. ex. la pollution par les nutriments et les produits chimiques). Enfin, nous proposons des priorités de recherche collaborative et interdisciplinaire pour faciliter la compréhension de ces mécanismes. Key Words: British Columbia; Citizen Science; coastal; monitoring; overwintering; Pacific; population trends; waterbirds; waterfowl

Address of Correspondent: Danielle Ethier, P.O. Box 160, 115 Front Road, Port Rowan, ON Canada N0E 1M0, Phone: 519-586-3531 ext. 115, [email protected] Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

INTRODUCTION species- and guild-specific trends in the Salish Sea and along the Human impacts on marine ecosystems are complex and outer Pacific coast. Specifically, we hypothesized that abundance widespread. Activities such as commercial fishing (e.g., Thrush et trends in waterbirds are influenced by dietary specialization and al. 1998), pollution (e.g., Kennish 2002), and climate change (e.g., migration distance. First, we predicted that abundance declines Harley et al. 2006) affect a diverse suite of flora and fauna, leading will be more prevalent in higher tropic feeders because this guild to complex and varying consequences for marine biodiversity. is generally more responsive to shifts in the availability and quality Unravelling these dynamic relationships and identifying the of prey (e.g., Ballance et al. 1997, Hyrenbach and Veit 2003, mechanisms driving declines in marine biodiversity continue to Ainley and Hyrenbach 2010, Vilchis et al. 2015). Second, we challenge ecologists (Möllmann and Diekmann 2012, Gamfeldt et predicted that abundance declines will be more pronounced in al. 2015). Comprehensive long-term monitoring programs that migrants because these populations are able to shift their range track ecosystem-wide trends in biodiversity and abundance are in response to resource availability more readily than local invaluable to this process because they provide information about breeders can (e.g., Burger and Gochfeld 1991, Marks and species in decline, their commonalities, and correlations with the Redmond 1994, Willie et al. 2020). Finally, we discuss potential hypothesized responsible drivers. Waterbirds are often considered mechanisms to stimulate future research and to inform to be ideal indicators of changes in marine productivity and conservation planning. ecosystem function across broad spatial and temporal scales because they are typically long-lived, migratory, and higher METHODS trophic-level feeders (Ainley and Hyrenbach 2010, Vilchis et al. 2015). Trends in waterbird abundance can therefore offer insights Study area into ecosystem changes happening locally and beyond and the The survey area extends from the north of Graham Island (54° conservation measures necessary to mitigate them. 02’36.3” N, 131°54’38.3” W) to the southern tip of Vancouver Island, Canada (48°19’04.3” N, 123°33’28.6” W; Fig. 1). There The coastline of British Columbia (BC), Canada, is home to are 326 survey routes in total, which cover a wide variety of diverse and plentiful marine life, including many globally types, including: rocky shores, sandy beaches, salt marshes, important staging, molting, and wintering areas for waterbirds that mudflats, fast-flowing channels, and other inshore waters. The migrate along the Pacific Flyway (e.g., Important Bird and BC coast experiences the mildest winters in all of Canada, with Biodiversity Areas in Canada: https://www.ibacanada.com/). The temperatures rarely dropping below freezing (https://www. Salish Sea supports 172 bird species that are dependent on the welcomebc.ca/Choose-B-C/Explore-British-Columbia/Climate-of- region’s , of which 72 are highly dependent on intertidal B-C). As a result, offshore and most inshore waters never freeze and marine habitats (Gaydos et al. 2008, Gaydos and Pearson completely, making the coastline and freshwater inflows attractive 2011). This coastline also supports large urban populations, to many wintering waterbirds that breed inland and further north. specifically in the south (e.g., Greater Vancouver Region), and maintains a strong economy based on ocean-based industries, which contribute $11 billion (8%) to the provincial gross domestic Fig. 1. Map of the British Columbia Coastal Waterbird Survey product (Stocks and Vandeborne 2017). Over the past two decades, (BCCWS) study area in British Columbia, Canada. The study the coastal human population of BC has increased by area was divided into two district regions: the inner coastal approximately 15,000 people/yr (1.21%; BC Stats 2020), which is waters of the Salish Sea (A), and the outer costal waters of the coupled with the expansion of ocean-based industries, including Pacific Ocean (B). Red dots denote the location of survey (in of importance): recreation, transportation, and seafood routes used to collect standardized counts of waterbirds from (Stocks and Vandeborne 2017). Along with the effects of global 1999–2019. climate change on ocean productivity (e.g., Moore et al. 2018), BC’s coastal and marine ecosystems are experiencing increasing pressures. Waterbird species that overwinter along BC’s coastline have similarly experienced significant changes in abundance in recent decades (Anderson et al. 2009, Bower 2009, Crewe et al. 2012), the causes of which remain largely unresolved. In 1999, Canada (formerly Bird Studies Canada) began the British Columbia Coastal Waterbird Survey (BCCWS) to collect baseline information on the status of waterbirds along the BC coast so that the impacts of natural and human-induced environmental change could be assessed through time. Here, we provide an update to the species-specific trend analysis done by Crewe et al. (2012) that marks 20 years of data collection by the BCCWS. In addition to analyzing abundance trends of species occupying the Canadian extent of the Salish Sea (inner coastal), we also assess trends from the outer coastal region of the Pacific Ocean (see Methods: Study area) to gain insight into the differential pressures facing birds using the two regions. Further, our analysis assesses the ecological characteristics associated with Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

We divided the study area into two distinctive regions: (1) the combined for the analysis (Scaup spp.) because of model Canadian extent of the Salish Sea (hereafter, Salish Sea), and (2) convergence issues when they were run independently, which were the outer coastal region of the Pacific Ocean (hereafter, Pacific resolved when counts were combined. In general, A. marila is coast). The Salish Sea survey routes are within the Straits of much more numerous than A. affinis along BC coastlines in winter Georgia and Juan de Fuca (Fig. 1A) and are comparable to those (e.g., Badzinski et al. 2006). The resulting data set included an used by Crewe et al. (2012) to permit direct trend comparison. ecologically and phylogenetically diverse suite of 50 species in the This region faces disproportionately high levels of environmental Salish Sea and 37 species along the outer Pacific coast that we pressure caused by the region’s large and rapidly growing human considered the core wintering coastal waterbird community of population and ocean-based industries (Georgia Strait Alliance, the BCCWS (Table 1). Based on Davidson et al. (2015) and expert About the Strait: https://georgiastrait.org/issues/about-the- review, we categorized migration distance for each species as: (1) strait-2/). The Pacific coast survey routes are those along the west local, i.e., regularly breeding in at least small numbers within the coast of Vancouver Island and routes within the Johnstone and study area catchment, (2) short distance, i.e., regularly breeding Hecate Straits (Fig. 1B). These coastal regions are sparsely in at least small numbers in the interior of BC, adjacent populated by rural coastal communities and experience northwestern , or the southeast Alaskan coast, or substantially less commercial and industrial pressure (Stocks amd (3) long-distance migrant, i.e., breeding in the northern Boreal Vandeborne 2017). and regions of . Species were also classified based on their dietary specialization following Bower (2009) and Data collection Billerman et al. (2020) as being benthivorous, piscivorous, From 1999–2019, surveys were conducted by volunteers using a herbivorous, or omnivorous (Appendix 1). standardized protocol and data collection sheets (Birds Canada 2018). Shore-based counts were completed monthly on or near Trends analysis the second Sunday of each month from September to April. Twenty-year trends in counts were estimated independently for Surveys were completed within approximately 2 h of high tide to each species and region using a Bayesian framework with maximize the opportunity for close observation. All waterbirds integrated nested Laplace approximation (INLA; Rue et al. 2009) observed to a distance of 1 km from the high tide line were in R (version 3.5.3; R Core Team 2014). Model comparison using counted, except those that flew through without stopping. In the leave-one-out cross-validation in INLA was used to select case of larger flocks, numbers were estimated by counting between a Poisson and negative binomial distribution (Held et al. individuals and species in groups and scaling up (see Birds Canada 2010). Count data were fit using a log-linear regression model for 2013). Surveyors varied within and among years, and because skill each species that included a continuous effect for year (t) to level was not recorded, observer skill was assumed to vary estimate the change in population size on a given route (j) over randomly and not systematically over time. Data were entered time (i.e., linear trend), a hierarchical first-order autoregressive through a customized online data entry system available on the term to model the temporal autocorrelation structure of residuals Birds Canada website, NatureCounts (https://www.birdscanada. among years (γ), and an independent and identically distributed org/birdmon/default/main.jsp). Observations were processed hierarchical term to account for random variation in counts using the eBird data filters to flag rare species and high counts among routes (η). during observer data entry (Cornell Laboratory help center: (1) https://support.ebird.org/en/support/solutions/articles/48000795278- log(μtj) = α + β1 * yeartj + γt + ηj the--review-process), and records were manually reviewed for form accuracy. The number of routes detecting a species each year was included as an offset to account for variable count effort and distributional Analysis metric differences across the study area. The continuous year coefficients The basic statistical unit for all analyses was the mean count of and credible intervals were transformed into constant rates of each species on a survey route across months within the species- population change using 100 × (exp(estimate) − 1). Annual indices specific survey window. Species-specific survey windows were of population size for each species were derived from the model assigned based on local knowledge of the months in the for the full 20-yr monitoring period. The analytical approach nonbreeding season that each species is most prevalent (Appendix applied here follows that of Crewe et al. (2012) to enable more 1). For example, the mean route-level count of Canada Goose direct comparison of trends, with some adjustment to improve (Branta canadensis) in a given year was calculated based on the analytical rigor. Specifically, both methods used a log-linear sum of monthly counts in December, January, and February regression model with continuous year and categorical route-level divided by the total number of months (N = 3). Only routes effects. Our model differed in that we deployed our analysis in a surveyed a minimum of 5 years and with 100% monthly coverage Bayesian framework and included additional hierarchical terms within the species-specific survey window were included in the to account for residual variation and an offset to account for analyses (e.g., December–February for most wintering birds). variation in sampling effort. The inclusion of a hierarchical term Because our aim was to focus on species that are persistent, here better accounts for temporal autocorrelation structure of abundant, and biologically associated with the study area, we residuals among years, thus allowing the model to better meet the excluded rarely detected species from our analyses (i.e., species assumption of sampling independence. Ignoring this dependency with > 85% zero counts across all routes and years, species that can make the estimates of standard error too small. Further, the had a mean abundance per year < 10, and species that were addition of an offset better ensures that changes in effort are detected in fewer than one-half of the survey years). Counts of accounted for during the analysis of trends. Greater Scaup (Aythya marila) and Lesser Scaup (A. affinis) were Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

Table 1. Annual population trends for 50 coastal waterbird species overwintering in the Salish Sea (inner coastal) and 37 species in the outer coast regions of the Pacific Ocean in British Columbia, Canada, from 1999–2019 and 1999–2011 (Crewe et al. 2012). Bold font indicates species for which a statistically significant annual trend (%/yr) is implied, i.e., lower credibility intervals (LCI) and upper credibility intervals (UCI) do not contain zero.

Common name Scientific name Salish Sea (1999–2019) Pacific coast (1999–2019) Salish Sea (1999–2011) Trend LCI UCI Trend LCI UCI Trend† Brant† Branta bernicla +0.10 −5.92 +5.44 −4.70 Canada Goose Branta canadensis +4.92 +2.84 +7.04 +1.91 −5.82 +9.96 −8.90 Trumpeter Swan† Cygnus buccinator −8.24 −12.01 −4.40 −1.49 −11.49 +8.00 −5.50 Gadwall Mareca strepera −0.30 −5.07 +4.92 −7.30 Eurasian Wigeon Mareca penelope −1.98 −9.43 +6.72 +14.11 −5.54 +37.03 +5.70 American Wigeon† Mareca americana +1.31 −0.90 +3.67 +9.20 −2.76 +23.24 +1.20 Mallard platyrhynchos +1.01 −1.39 +3.56 +3.67 −3.73 +9.97 −1.10 Northern Pintail† Anas acuta −2.96 −14.70 +8.76 +15.37 −5.92 +41.20 −2.60 Green-winged Teal Anas crecca −0.70 −3.82 +2.74 +7.79 −4.59 +21.05 −7.90 Ring-necked Duck Aythya collaris +10.63 +5.13 +15.95 +4.70 Scaup spp. Scaup sp. −10.68 −13.58 −7.69 −8.15 −28.82 +16.77 Greater −9.80 Lesser −14.50 † Histrionicus histrionicus −0.70 −1.98 +0.70 −4.97 −11.40 +2.22 −2.60 Surf † Melanitta perspicillata −2.27 −4.02 −0.50 +3.77 −9.79 +17.00 −7.60 White-winged Scoter† Melanitta deglandi −4.30 −7.50 −0.60 +7.57 −4.02 +20.68 −7.60 Melanitta americana −14.96 −18.29 −11.49 −19.20 Long-tailed Duck Clangula hyemalis −5.07 −8.42 −1.59 +6.72 −3.54 +19.84 −7.00 Bufflehead Bucephala albeola +0.60 −1.09 +2.63 +1.11 −5.54 +8.44 −0.70 Common Bucephala clangula −0.50 −2.37 +1.31 +5.23 −4.11 +13.20 −0.20 Barrow’s Goldeneye Bucephala islandica −2.37 −4.88 +1.31 −8.15 −14.87 −0.60 −4.30 Hooded Merganser Lophodytes cucullatus −0.90 −3.82 +2.02 −5.82 −9.34 −2.08 Common Merganser merganser +2.94 −0.60 +6.93 +0.60 −8.06 +8.22 +1.70 Red-breasted Merganser† Mergus serrator −0.70 −3.25 +2.12 −1.19 −6.85 +4.29 −0.60 Horned Grebe Podiceps auritus +1.51 −2.18 +4.92 +6.40 −2.57 +15.26 −2.60 Red-necked Grebe† Podiceps grisegena +1.92 −4.40 +9.53 +7.57 +1.31 +13.20 −2.90 Western Grebe† Aechmophorus occidentalis −12.72 −17.47 −7.69 −0.80 −14.02 +14.00 −16.40 Black Oystercatcher† Haematopus bachmani +1.21 −3.92 +4.81 +0.90 Black-bellied Plover† Pluvialis squatarola −2.18 −8.52 +3.77 −4.00 Killdeer Charadrius vociferus +2.22 −4.69 +9.09 +7.90 −7.87 +26.49 −2.60 Black † Arenaria melanocephala −4.21 −7.87 −0.90 +0.70 −9.24 +11.74 +0.40 Surfbird† virgata −5.54 −14.44 +4.39 −18.10 Dunlin† Calidris alpina −9.70 −13.06 −6.01 +5.76 −11.13 +25.48 −8.90 Greater Yellowlegs melanoleuca −4.21 −9.24 +1.21 −10.50 Common Murre Uria aalge +3.15 −3.92 +10.85 +13.66 +0.70 +28.40 +3.80 Pigeon Guillemot Cepphus columba −3.54 −10.95 +4.39 +16.65 −0.60 +38.13 +21.70 Marbled Murrelet† Brachyramphus marmoratus +3.36 −1.29 +8.00 −7.50 −16.72 +2.74 −4.40 Bonaparte’s Gull† Chroicocephalus philadelphia −2.47 −9.79 +5.55 −12.90 Heermann’s Gull Larus heermanni −3.82 −13.93 +7.04 Mew Gull Larus canus −4.59 −10.33 −0.50 +4.50 −3.54 +12.98 −2.50 Ring-billed Gull Larus delawarensis −2.57 −7.32 +2.53 −0.90 Gull Larus californicus +1.01 −5.45 +8.00 −8.90 Thayer’s Gull† Larus glaucoides −3.54 −7.60 +0.60 −4.11 −18.21 +12.86 −4.10 Glaucous-winged Gull† Larus glaucescens −0.90 −3.44 +1.41 −2.27 −8.70 +4.08 −4.30 Red-throated † Gavia stellata −4.59 −10.68 +1.82 −9.30 Pacific Loon† Gavia pacifica −6.01 −9.88 −1.88 −4.50 −11.93 +4.81 −6.30 Gavia immer −2.96 −4.97 −0.90 +2.22 −1.49 +6.29 −2.80 Pelagic Cormorant† Phalacrocorax pelagicus +0.80 −4.02 +6.61 +3.46 −2.57 +8.87 +1.80 Double-crested Cormorant Phalacrocorax auritus −1.98 −5.26 +2.12 +1.01 −7.04 +9.31 −0.40 Great Blue Heron Ardea herodias +1.41 −2.37 +6.40 −6.76 −11.75 −1.78 −3.00 Bald Eagle Haliaeetus leucocephalus +0.50 −1.69 +2.74 +1.11 −1.78 +4.08 −1.80 Belted alcyon 0.00 −4.69 +4.50 −3.92 −13.06 +5.44 †Crewe et al. (2012). †Species that occur in globally significant numbers along the British Columbia coast (BirdLife International 2020; Important Bird and Biodiversity Areas in Canada: https://www.ibacanada.com/).

The guild analysis was done using the same framework as distributed hierarchical term was included to account for random previously described for species-specific trends, fitting a separate variation in counts among species. The number of routes surveyed model for migration distances and dietary categorizations for within a given year was included as an offset to account for each region. An additional independent and identically differences in sampling effort. Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

RESULTS DISCUSSION Species-specific trends (annual rates of change) over the past 20 Our results highlight several themes, including species-specific years of the BCCWS are displayed in Table 1 (see also Appendices trends of importance to management agencies, 12-yr vs. 20-yr 2 and 3) for both the Salish Sea and Pacific coast. Trends are trajectory comparisons within the Canadian Salish Sea, and considered statistically significant when credibility intervals (CIs) regional differences in guild-specific abundance patterns, which do not overlap zero. Data suggest that most populations are stable can better inform future targeted research and conservation (i.e., trends are not significant) in both the Salish Sea (36 of 50 initiatives. spp.) and Pacific coast (32 of 37 spp.) regions. Twelve species displayed significant decline trends in the Salish Sea, whereas two Species-specific trends had significant increases (Canada Goose; Ring-necked Duck, Eight taxa maintained significant negative abundance trajectories Aythya collaris). Along the Pacific coast, only three species in the Canadian Salish Sea over the last 20 years (i.e., declining displayed significant decline trends (Barrow’s Goldeneye, trends reported by Crewe et al. 2012 continued): Scaup spp., Bucephala islandica; Hooded Merganser, Lophodytes cucullatus; White-winged Scoter (Melanitta deglandi), Black Scoter and Great Blue Heron, Ardea herodiasand) and two showed (Melanitta americana), Long-tailed Duck (Clangula hyemalis), significant increases (Common Murre, Uria aalge and Red- Western Grebe (Aechmophorus occidentalis), Dunlin (Calidris necked Grebe, Podiceps grisegena). Markedly, there was no alpina), Common Loon (Gavia immer), and Pacific Loon (Gavia overlap in the species displaying significant trends between the pacifica). All of these species are longer distance migrants and two study regions. upper trophic-level feeders (i.e., piscivorous or benthivorous), except Scaup spp. (omnivorous). Conversely, along the outer Guild-specific trends indicate that communities of overwintering Pacific coast, all these species demonstrated stable trajectories. waterbirds occupying the Salish Sea are doing significantly less Four additional species in the Salish Sea, which showed stable well than those residing along the outer Pacific coast, almost trends from 1999–2011 (Crewe et al. 2012), demonstrated irrespective of dietary specialization or migration distance (Fig. significant negative trends over the 20-year period: Black 2). Specifically, all dietary guilds in the Salish Sea, except for Turnstone (Arenaria melanocephala), Surf Scoter (Melanitta herbivores, experienced significant negative trends in abundance perspicillata), Mew Gull (Larus californicus), and Trumpeter from 1999–2019. The steepest declines were in benthivores (%/yr: Swan (Cygnus buccinator). Each of these taxa are longer distance −4.02; CI: −5.92, −2.18) and long-distance migrants (−4.02; migrants, except for Trumpeter Swan, and two are benthivorous −5.92, −2.18). In contrast, waterbird guilds along the outer Pacific (Appendix 1). Similarly, none of these taxa demonstrated declines coast experienced significant increases, apart from benthivores along the outer Pacific coast. Species that demonstrated (2.22; −0.40, 4.81) and omnivores (−1.29; −5.07, 2.22), whose significant increases in abundance include overwintering trends were stable. populations of Canada Goose and Ring-necked Duck (Aythya collaris) within the Salish Sea (herbivorous and omnivorous, Fig. 2. Abundance trends of waterbirds with similar dietary respectively), and Red-necked Grebe (Podiceps grisegena) and requirements (left panel) and migration strategies (right panel) Common Murre (Uria aalge) along the outer Pacific coast (both surveyed from 1999–2019 in the Salish Sea (grey) and outer piscivorous). These species are all local breeders or short-distance coastal regions of the Pacific Ocean (black), British Columbia, migrants. In summary, 7 of the 12 negatively trending taxa are Canada. Guilds are defined on the y-axis, with migration types benthivorous on their Salish Sea wintering grounds; Common comprising long-distance migrants (LDM), short-distance Loon (piscivorous) and Scaup spp. (omnivorous) also feed in the migrants (SMD), and local breeders (Local). Annual percent benthic environment in winter (Evers et al. 2020, Kessel et al. change and credibility intervals (CI) are displayed on the x-axis. 2020). The guild-specific analysis further corroborates the A statistically significant annual trend is implied when upper observed species-specific trends found in benthivores in the Salish and lower CIs do not overlap zero (dashed vertical line). Sea (Fig. 2). Notwithstanding the fact that many of the benthivorous taxa show declining trends in other parts of their continental and global ranges (Billerman et al. 2020, IUCN 2020), these results suggest that benthic habitat quality in the Salish Sea may deserve further targeted research attention (see Discussion: Guild-specific trends). The only two species to show increases in the Salish Sea were a lower abundance generalist (omnivorous) and a population augmented by previous introductions (Canada Goose; e.g., Isaac-Renton et al. 2010). The piscivore guild has previously been shown to be at highest risk of decline within the Salish Sea, linked to declines in forage (Vilchis et al. 2015), so it is interesting to note the increases in these two piscivores along the Pacific coast. Comparison of our 20-year Salish Sea results with those from Crewe et al. (2012) also show some notable positive differences in species-specific abundance trends, which can be expected given that waterbird populations fluctuate quite widely over decadal time frames (e.g., Wilkins and Otto 2003). Ten of twenty species Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

previously showing significant declines showed stable 20-yr (Calidris alpina pacifica) population winters here (Morrison et al. trends, which could be indicative of population stabilization or 2006; Important Bird and Biodiversity Areas in Canada: https:// growth since the previous analysis (Appendices 1–3). These www.ibacanada.com/). Dunlin (all subspecies) is also identified species include globally important populations of Harlequin as a high priority candidate species for assessment by the Duck (Histrionicus histrionicus), Surfbird (Calidris virgata), Committee on the Status of Endangered Wildlife in Canada Glaucous-winged Gull (Larus glaucescens), Bonaparte’s Gull (COSEWIC), which comprises taxa not yet assessed but where (Chroicocephalus philadelphia), and Red-throated Loon (Gavia new information suggests they may be at risk of extinction or stellata; BirdLife International, global IBA criteria: http:// extirpation (COSEWIC 2020). Black Turnstone, a rocky shore datazone.birdlife.org/site/ibacritglob). These inter-decadal trend specialist (benthivorous), and Pacific Loon (piscivorous) both comparisons can be informative to Canada’s federal 2002 Species showed 20-yr declines in the Salish Sea but stable trends on the at Risk Act process. Specifically, BCCWS data can be used to outer Pacific coast, contributing to the contrasting pattern inform both the listing process and recovery strategy evaluation. between benthic feeders and piscivores on inner and outer coasts. For example, Horned Grebe (Podiceps auratus) was listed One further taxon to draw attention to is Thayer’s Gull (Larus federally as a species of Special Concern based on evidence of a glaucoides thayeri); a large proportion of the global population 14% population decline in the previous three generations of this Canadian Arctic breeder winters in the Salish Sea and (COSEWIC 2009), including a declining trend in numbers showed a narrowly nonsignificant declining trend, after both 12 wintering in the Salish Sea. Our results show that since 2011, the years (Crewe et al. 2012) and 20 years (this study). numbers have stabilized or possibly increased. Great Blue Heron Although species-specific trends are informative and, in some (Ardea herodias fannini), also a taxon of Special Concern instances, likely represent true trends in total population (COSEWIC 2008), experienced abundance stabilization in the abundance, it is inherently difficult to interpret local changes in Salish Sea since 2011, compared to a significant declining trend the abundance of longer distance migratory waterbirds. This noted between 1999 and 2011 (Crewe et al. 2012). However, along difficulty is in part because local counts do not constitute an the Pacific coast, this subspecies had a 20-yr declining trend, exhaustive inventory of the population, nor do they cover the which suggests that differential pressures affect this species within species’ entire range. Specifically, abundance trends in one part the Canadian Salish Sea and along the Pacific coast. The BCCWS of a species’ range cannot discern if local fluctuations are driven is considered to have the most robust data for tracking abundance by shifting distributions or changing population numbers trends in this taxon because of the survey’s standardized data (Hyrenbach and Veit 2003). For example, the decline in Western collection procedures and robust statistical design (COSEWIC Grebe in the Salish Sea is ongoing but is explained at least partly 2008). by a southward nonbreeding range shift of nearly 900 km during Twenty-two species sampled by this survey occur in globally the past three decades (Wilson et al. 2013). To discern better if significant numbers along the BC coast (BirdLife International, trends are a result of range-wide population change or global IBA criteria: http://datazone.birdlife.org/site/ibacritglob; redistribution, the Migratory Shorebird Project was established Table 1); seven of these species experienced 20-yr declines in the in 2013 to sample nonbreeding populations of shorebirds along Salish Sea, and just one, Red-necked Grebe (Podiceps grisegena), the Pacific Coast of the Americas (Reiter et al. 2020). This a piscivore, showed an increasing trend on the Pacific coast only. hemispheric, hypothesis-driven monitoring framework, to which Several of these abundance trends are noteworthy. Declining sea the BCCWS is a contributing partner, will provide the context to ducks of global significance (e.g., Surf Scoter, White-winged better assess local causes of declines in shorebird species of Scoter) are part of the benthivore community considered above. conservation concern. A significant decline in Trumpeter Swan in the Salish Sea (−8.24; −12.01, −4.40) differs from regional trends reported elsewhere, Guild-specific trends which have noted abundance gains in recent decades (e.g., the Within the Salish Sea, our results support the prediction that Pacific Coast population increased 5.5%/yr from 1968–2005 and abundance declines are more prevalent in higher trophic-level 1.5%/yr from 2005–2010; Northwest Swan Conservation feeders, with significant declines experienced by all guilds except Association: https://nwswans.org/trumpeter-swans/). The BCCWS herbivores (Fig. 2). Our findings align with those of Vilchis et al. is not well designed to sample this swan (Crewe et al. 2012), which (2015) for piscivores and guilds without local breeding uses southern coastal agricultural lands for feeding by day and populations and, for the first time, highlight benthivores as the nearshore waters for roosting. However, these results may indicate guild showing steepest 20-yr declines. Putative mechanisms a change in trend trajectory in the Canadian Salish Sea after a behind these changes in abundance could include: redistribution period of conservation-driven increase and stabilization noted in response to prey (demonstrated for Western Grebe; Wilson et elsewhere (Rees et al. 2019). Continuing loss of winter habitat is al. 2013), redistribution in response to predators (e.g., Middleton identified as a major threat to this species (Trumpeter Swam et al. [2018] found that dive-feeding birds in the Salish Sea, Society, Pacific coast population: https://www.trumpeterswansociety. including , moved away from shore in response to the threat org/what-we-do/your-society-at-work/pacific-coast-population.html) from Bald Eagle Haliaeetus leucogaster), factors operating in as agricultural land use shifts toward more greenhouse and berry other parts of the ranges of longer distance migrants (e.g., crops instead of field crops that provide wintering waterfowl climate-driven changes in aquatic prey on boreal or habitat (British Columbia Ministry of Agriculture 2017). The arctic breeding grounds; e.g., Corcoran et al. 2009, Arzel et al. significant decline of Dunlin (−9.70; −13.06, −6.01) wintering in 2020), and changes to benthic and epibenthic food sources in the the Salish Sea flags a potential conservation issue for local Salish Sea. Duck species that have benefited from ongoing management agencies given that up to 20% of the Pacific Dunlin conservation investment in > 80,000 km² of wetlands and adjacent Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

lands in Canada, under the North American Waterfowl differential environmental and human-induced pressures than Management Plan (NABCI-Canada 2019), showed stable or those along the outer Pacific coast. For example, nutrient increasing species-specific trends in the Salish Sea, including pollution from rivers, nonpoint source runoff, and wastewater American Wigeon (Mareca americana), Northern Pintail (Anas sources have been recognized as primary threats to the ecological acuta), and Green-winged Teal (Anas crecca). At the guild level, health of the inner waters of the Salish Sea (Khangaonkar et al. these herbivores were the only group that showed a (narrowly) 2019). The effects of nutrient pollution on coastal ecosystems are stable trend (Fig. 2). exacerbated when coupled with projected future climate stressors, the negative effects of chemical pollution from industry and When combined, results from the Salish Sea and Pacific coasts municipalities, oil spills, invasive species, and increased pressures did not lend support to our guild-level hypotheses. Specifically, from shipping, fishing, recreation, and shoreline development, all there was no evidence that abundance declines were more of which are likely to affect the Salish Sea to a greater extent than prevalent in higher trophic-level feeders along the Pacific coast, the outer coastal waters of the Pacific Ocean (e.g., Stocks and where piscivores (8.11; 4.08, 12.30) experienced significant Vandeborne 2017). Collaborative research combining the abundance gains (Fig. 2). The prediction that longer distance BCCWS data set with compatible waterbird surveys (e.g., Puget migrants would be more susceptible to declines than local Sound Seabird Survey, Seattle Audubon: https://www. breeders was also unsupported; all three guilds (local breeders, seattleaudubon.org/sas/About/Science/CitizenScience/ short-distance and long-distance migrants) experienced PugetSoundSeabirdSurvey.aspx), monitoring levels of food abundance gains along the Pacific coast (Fig. 2). These guild- resources (e.g., plankton food web [Costalago et al. 2020], benthic specific results provide evidence of consistently contrasting surveys [Ranasinghe et al. 2013]), monitoring of rocky intertidal patterns within and outside the Salish Sea, suggesting that communities (e.g., Multi-agency Rocky Intertidal Network, differential pressures may be causing overall loss of wintering Washington Salish Sea sites: https://marine.ucsc.edu/sites/sites- waterbirds within, or abundance shifts away from, the Salish Sea, region/sites-region-wa.html), and integrated stakeholder participation a pattern already demonstrated for Western Grebe (Wilson et al. (Bayard et al. 2019) would enable the necessary hypothesis testing 2013). This finding should be of particular interest to agencies to improve the understanding of waterbird abundance trends and responsible for the bird populations and their habitats in the Salish the conservation actions needed in the Salish Sea and along the Sea, specifically Environment and Climate Change Canada, Pacific coast. Fisheries and Oceans Canada, the Government of British Columbia, the Pacific Birds Habitat and Sea Duck Joint Ventures, and Indigenous Governments. Canadian agencies share Responses to this article can be read online at: responsibility for management of the Salish Sea with agencies in https://www.ace-eco.org/issues/responses.php/1711 Puget Sound, Washington, USA, where one of the largest ecosystem restoration programs in the United States is underway (Puget Sound Partnership 2018). The results of seven years of citizen science data from the Puget Sound Seabird Survey, Acknowledgments: coordinated by the Seattle Audubon Society, were more The British Columbia Coastal Waterbird Survey was conceived by encouraging than ours. Ward et al. (2015) showed evidence of a group of scientists, local naturalists, and conservation planners, local increases in 14 of 18 species in Puget Sound, especially those and initiated in 1999 by Birds Canada. The survey is maintained with local breeding populations, and some commonalities in annually through funding from the Canadian Wildlife Service, a declining species with our 20-yr results (e.g., White-winged Scoter, branch of Environment and Climate Change Canada; additional Western Grebe), raising the possibility that localized active support has been provided by the Vancouver Foundation, BC restoration is a mechanism to consider in understanding changes Waterfowl Society, Public Conservation Assistance Fund of the in coastal waterbird abundances in other regions of the Salish Sea. Habitat Conservation Trust Foundation, TD Friends of the Environment Fund, The Port of Vancouver, and BC Field CONCLUSIONS Ornithologists. We thank the ~1600 volunteers that have collected Results from this study further demonstrate that citizen science data over the past 20 years who made this analysis possible. Two data provide robust insight into regional abundance trends of anonymous reviewers provided valuable input, which improved the coastal waterbirds and the commonalities that influence their clarity of our manuscript. susceptibility to environmental pressures (Bower 2009, Vilchis et al. 2015). These abundance trends are important for evaluating the status of vulnerable and ecologically significant populations LITERATURE CITED (e.g., COSEWIC, Pacific America’s Shorebird Conservation Ainley, D. G., and K. D. Hyrenbach. 2010. Top-down and Strategy, Important Bird and Biodiversity Areas), and bottom-up factors affecting seabird population trends in the establishing baseline statistics against which policy changes can California current system (1985–2006). Progress in Oceanography be evaluated (e.g., oil spill monitoring; O’Hara et al. 2009). Long- 84(3-4):242-254. https://doi.org/10.1016/j.pocean.2009.10.001 term citizen science monitoring of coastal ecosystems provides a foundation from which to tease apart whether local population Anderson, E. M., J. L. Bower, D. R. Nysewander, J. R. Evenson, fluctuations are a result of true changing abundance or shifts in and J. R. Lovvorn. 2009. Changes in avifaunal abundance in a species distributions over time (Vilchis et al. 2015, Reiter et al. heavily used wintering and migration site in Puget Sound, 2020) and to resolve the mechanisms responsible (e.g., Bianchini Washington, During 1966–2007. Marine Ornithology 37:19-27. et al. 2020). Organisms living in the Salish Sea are exposed to [online] URL: https://www.marineornithology.org/PDF/37_1/37_1_19-27. pdf Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

Arzel, C., P. Nummi, L. Arvola, H. Pöysä, A. Davranche, M. Burger, J., and M. Gochfeld. 1991. Human distance and birds: Rask, M. Olin, S. Holopainen, R. Viitala, E. Einola, and S. tolerance and response distances of resident and migrant species Manninen-Johansen. 2020. are declining in boreal in India. Environmental Conservation 18(2):158-165. https://doi. aquatic habitat: the effect of brownification? Science of the Total org/10.1017/S0376892900021743 Environment 724:138199. https://doi.org/10.1016/j.scitotenv.2020.138199 Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 2008. COSEWIC assessment and update status Badzinski, S. S., R. J. Cannings, T. E. Armenta, J. Komaromi, and report on the Great Blue Heron Ardea herodias fannini, fannini P. J. A. Davidson. 2006. The British Columbia coastal waterbird subspecies, in Canada. COSEWIC, Ottawa, Canada. [online] survey: an evaluation of survey power and species trends after five URL: https://www.sararegistry.gc.ca/virtual_sara/files/cosewic/ years of monitoring. Technical Report Series 455. Canadian sr_great_blue_heron_0808_e.pdf Wildlife Service, Pacific and Yukon Region, Delta, Canada. [online] URL: http://publications.gc.ca/collections/collection_2018/ Committee on the Status of Endangered Wildlife in Canada eccc/cw69-5/CW69-5-455-eng.pdf (COSEWIC). 2009. COSEWIC assessment and status report on the Horned Grebe Podiceps auritus, Western population and Ballance, L. T., R. L. Pitman, and S. B. Reilly. 1997. Seabird Magdalen Islands population, in Canada. COSEWIC, Ottawa, community structure along a productivity gradient: importance Canada. [online] URL: https://www.sararegistry.gc.ca/virtual_sara/ of competition and energetic constraint. Ecology 78 files/cosewic/sr_horned_grebe_0809_e.pdf (5):1502-1518. https://doi.org/10.1890/0012-9658(1997)078[1502: SCSAAP]2.0.CO;2 Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 2020. COSEWIC candidate wildlife species. Bayard, T., G. Slater, K. Spragens, and A. Summers. 2019. COSEWIC, Ottawa, Canada. [online] URL: http://www.cosewic. Recommendations for a Puget Sound estuary avian monitoring ca/index.php/en-ca/reports/candidate-wildlife-species strategy. A synthesis report to the Puget Sound Ecosystem Monitoring Program and Puget Sound Partnership. Audubon, Corcoran, R. M., J. R. Lovvorn, and P. J. Heglund. 2009. Long- Tacoma, Washington, USA. [online] URL: https://wa.audubon. term change in limnology and invertebrates in Alaskan boreal org/sites/default/files/static_pages/attachments/bayard_et_al._2019. wetlands. Hydrobiologia 620:77-89. https://doi.org/10.1007/ _ s10750-008-9616-5 recommendations_avian_monitoring_strategy_puget_sound_estuaries. Costalago, D., I. Forster, N. Nemcek, C. Neville, R. I. Perry, K. pdf Young, B. P. V. Hunt. 2020. Seasonal and spatial dynamics of the BC Stats. 2020. British Columbia - population estimates. planktonic trophic biomarkers in the Strait of Georgia (northeast Government of British Columbia, Victoria, Canada. [online] Pacific) and implications for fish. Scientific Reports 10:8517. URL: https://bcstats.shinyapps.io/popApp/ https://doi.org/10.1038/s41598-020-65557-1 Bianchini, K., D. C. Tozer, R. Alvo, S. P. Bhavsar, and M. L. Crewe, T., K. Barry, P. Davidson, and D. Lepage. 2012. Coastal Mallory. 2020. Drivers of declines in common loon (Gavia immer) waterbird population trends in the Strait of Georgia 1999–2011: productivity in Ontario, Canada. Science of the Total Environment results from the first 12 years of the British Columbia coastal 738:139724. https://doi.org/10.1016/j.scitotenv.2020.139724 waterbird survey. British Columbia Birds 22:8-39. [online] URL: https://bcbirds.bcfo.ca/volume-22-3/ Billerman, S. M., B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg, editors. 2020. Birds of the world. Cornell Laboratory Davidson, P. J. A., R. J. Cannings, A. R. Couturier, D. Lepage, of Ornithology, Ithaca, New York, USA. [online] URL: https:// and C. M. Di Corrado, editors. 2015. Atlas of the breeding birds doi.org/10.2173/bow of British Columbia, 2008–2012. Bird Studies Canada, Delta, Canada. [online] URL: http://www.birdatlas.bc.ca/ Birds Canada. 2013. BC coastal waterbird survey: training module for volunteers. Birds Canada, Port Rowan, Canada. [online] URL: Evers, D. C., J. D. Paruk, J. W. McIntyre, and J. F. Barr. 2020. https://www.birdscanada.org/wp-content/uploads/2020/02/BCCWS- Common Loon (Gavia immer), version 1.0. In S. M. Billerman, Training-Module.pdf editor. Birds of the world. Cornell Laboratory of Ornithology, Ithaca, New York, USA. [online] URL: https://doi.org/10.2173/ Birds Canada. 2018. BC coastal waterbird survey protocol: bow.comloo.01 instructions for participants. Birds Canada, Port Rowan, Canada. [online] URL: https://www.birdscanada.org/wp-content/uploads/2020/02/ Gamfeldt, L., J. S. Lefcheck, J. E. K. Byrnes, B. J. Cardinale, J. E. BCCWS-Protocol.pdf Duffy, and J. N. Griffin. 2015. Marine biodiversity and ecosystem functioning: What’s known and what’s next? Oikos 124 Bower, J. L. 2009. Changes in marine bird abundance in the Salish (3):252-265. https://doi.org/10.1111/oik.01549 Sea: 1975 to 2007. Marine Ornithology 37:9-17. [online] URL: http://www.marineornithology.org/PDF/37_1/37_1_9-17.pdf Gaydos, J. K., L. Dierauf, G. Kirby, D. Brosnan, K. Gilardi, and G. E. Davis. 2008. Top 10 principles for designing healthy coastal British Columbia Ministry of Agriculture. 2017. Agriculture in ecosystems like the Salish Sea. EcoHealth 5:460. https://doi. brief: Fraser Valley regional district 2016. British Columbia org/10.1007/s10393-009-0209-1 Ministry of Agriculture, Victoria, Canada. [online] URL: https:// www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/ Gaydos, J. K., and S. F. Pearson. 2011. Birds and mammals that agriculture-and-seafood/statistics/census/census-2016/ depend on the Salish Sea: a compilation. Northwestern Naturalist aginbrief_2016_fraser_valley.pdf 92(2):79-94. https://doi.org/10.1898/10-04.1 Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

Harley, C. D. G., A. R. Hughes, K. M. Hultgren, B. G. Miner, C. Study Group Bulletin 111:67-85. [online] URL: https://www. J. B. Sorte, C. S. Thornber, L. F. Rodriguez, L. Tomanek, and S. waderstudygroup.org/article/3068/ L. Williams. 2006. The impacts of climate change in coastal North American Bird Conservation Initiative Canada (NABCI- marine systems. Ecology Letters 9(2):228-241. https://doi. Canada). 2019. The state of Canada’s birds: 2019. NABCI- org/10.1111/j.1461-0248.2005.00871.x Canada, Gatineau, Canada. [online] URL: http://nabci.net/wp- Held, L., B. Schrödle, and H. Rue. 2010. Posterior and cross- content/uploads/2019-State-of--Birds-1.pdf validatory predictive checks: a comparison of MCMC and INLA. O’Hara, P. D., P. Davidson, and A. E. Burger. 2009. Aerial Pages 91-110 in T. Kneib and G. Tutz, editors. Stastical modelling surveillance and oil spill impacts based on beached bird survey and regression studies: festschrift in honour of Ludwig Fahrmeir. data collected in southern British Columbia. Marine Ornithology Physica, Heidelberg, Germany. https://doi.org/10.1007/978-3-79­ 37:61-65. [online] URL: http://www.marineornithology.org/ 08-2413-1_6 PDF/37_1/37_1_61-65.pdf Hyrenbach, K. D., and R. R. Veit. 2003. Ocean warming and Puget Sound Partnership. 2018. The 2018–2022 action agenda for seabird communities of the southern California Current System Puget Sound. Puget Sound Partnership, Olympia, Washington, (1987–98): response at multiple temporal scales. Deep Sea USA. [online] URL: https://pspwa.app.box.com/s/ Research Part II: Topical Studies in Oceanography 50 osxaeqg19fevxu5n3k8xnjytzkwol512 (14-16):2537-2565. https://doi.org/10.1016/S0967-0645(03)00123-1 R Core Team. 2014. R: a language and environment for statistical International Union for Conservation of Nature (IUCN). 2020. computing. R Foundation for Statistical Computing, Vienna, The IUCN Red List of threatened species. Version 2020-2. IUCN, Austria. Cambridge, UK. [online] https://www.iucnredlist.org/ Ranasinghe, J. A., E. D. Stein, M. R. Frazier, and D. J. Gillett. Isaac-Renton, M., J. R. Bennett, R. J. Best, and P. Arcese. 2010. 2013. Development of Puget Sound benthic indicators: report to the Effects of introduced Canada geese (Branta canadensis) on native Washington State Department of Ecology. SCCWRP Technical plant communities of the southern Gulf Islands, British Report 755. Washington State Department of Ecology Columbia. Écoscience 17(4):394-399. https://doi.org/10.2980/17-4-3332 Publication 13-03-035. Washington State Department of Ecology, Olympia, Washington, USA. [online] URL: https:// Kennish, M. J. 2002. Environmental threats and environmental fortress.wa.gov/ecy/publications/documents/1303035.pdf future of estuaries. Environmental Conservation 29(1):78-107. Rees, E. C., L. Cao, P. Clausen, J. T. Coleman, J. Cornely, O. https://doi.org/10.1017/S0376892902000061 Einarsson, C. R. Ely, R. T. Kingford, M. Ma, C. D. Mitchell, S. Kessel, B., D. A. Rocque, and J. S. Barclay. 2020. Greater Scaup Nagy, T. Shindad, J. Snyder, D. V. Solovyeva, W. Tijsen, Y. A. (Aythya marila), version 1.0. In S. M. Billerman, editor. Birds of Vilina, R. Włodarczyk, and K. Brides. 2019. Conservation status the world. Cornell Laboratory of Ornithology, Ithaca, New York, of the world’s swan population, Cygnus sp. and Coscoroba sp.: a USA. https://doi.org/10.2173/bow.gresca.01 review of current trends and gaps in knowledge. Wildfowl 5:35-72. [online] URL: https://wildfowl.wwt.org.uk/index.php/wildfowl/ Khangaonkar, T., A. Nugraha, W. Xu, and K. Balaguru. 2019. article/view/2705 Salish Sea response to global climate change, sea level rise, and future nutrient loads. Journal of Geophysical Research: Oceans Reiter, M. E., E. Palacios, D. Eusse-Gonzalez, R. Johnston, P. 124(6):3876-3904. https://doi.org/10.1029/2018JC014670 Davidson, D. W. Bradley, R. Clay, K. M. Strum, J. Chu, B. A. Barbaree, C. M. Hickey, D. B. Lank, M. Drever, R. C. Ydenberg, Marks, J. S., and R. L. Redmond. 1994. Migration of bristle- and R. Butler. 2020. A monitoring framework for assessing threats thighed on Laysan Island: timing, behavior and estimated to nonbreeding shorebirds on the Pacific coast of the Americas. flight range. Condor 96(2):316-330. https://doi.org/10.2307/1369317 Avain Conservation and Ecology 15(2):7. https://doi.org/10.5751/ ACE-01620-150207 Middleton, H. A., R. W. Butler, and P. Davidson. 2018. Waterbirds alter their distribution and behavior in the presence of bald eagles Rue, H., S. Martino, and N. Chopin. 2009. Approximate Bayesian (Haliaeetus leucocephalus). Northwestern Naturalist 99(1):21-30. inference for latent Gaussian models by using integrated nested https://doi.org/10.1898/nwn16-21.1 Laplace approximations. Journal of the Royal Statistical Society: Series B 71(2):319-392. https://doi.org/10.1111/j.1467-9868.2008.00700. Möllmann, C., and R. Diekmann. 2012. Marine ecosystem regime x shifts induced by climate and overfishing: a review for the Northern Hemisphere. Advances in Ecological Research Stocks, A., and K. Vandeborne. 2017. The state of coastal 47:303-347. https://doi.org/10.1016/B978-0-12-398315-2.00004-1 communities in British Columbia. T. Buck Suzuki Environmental Foundation, Victoria, Canada. [online] URL: https:// Moore, J. K., W. Fu, F. Primeau, G. L. Britten, K. Lindsay, M. d3n8a8pro7vhmx.cloudfront.net/tbucksuzuki/pages/158/attachments/ Long, S. C. Doney, N. Mahowald, F. Hoffman, and J. T. original/1576611259/The_State_of_Coastal_Communities_in_B­ Randerson. 2018. Sustained climate warming drives declining ritish_Columbia_2017.pdf?1576611259 marine biological productivity. Science 359:1139-1143. https:// Thrush, S. F., J. E. Hewitt, V. J. Cummings, P. K. Dayton, M. doi.org/10.1126/science.aao6379 Cryer, S. J. Turner, G. A. Funnell, R. G. Budd, C. J. Milburn, and Morrison, R. I. G., B. J. McCaffery, R. E. Gill, S. K. Skagen, S. M. R. Wilkinson. 1998. Disturbance of the marine benthic habitat L. Jones, G. W. Page, C. L. Gratto-Trevor, and B. A. Andres. 2006. by commercial fishing: impacts at the scale of the fishery. Population estimates of North American shorebirds, 2006. Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/

Ecological Applications 8(3):866-879. https://doi.org/10.1890/1051-0761 (1998)008[0866:DOTMBH]2.0.CO;2 Vilchis, L. I., C. K. Johnson, J. R. Evenson, S. F. Pearson, K. L. Barry, P. Davidson, M. G. Raphael, and J. K. Gaydos. 2015. Assessing ecological correlates of marine bird declines to inform marine conservation. Conservation Biology 29(1):154-163. https:// doi.org/10.1111/cobi.12378 Ward, E. J., K. N. Marshall, T. Ross, A. Sedgley, T. Hass, S. F. Pearson, G. Joyce, N. J. Hamel, P. J. Hodum, and R. Faucett. 2015. Using citizen-science data to identify local hotspots of seabird occurrence. PeerJ 3:e704. https://doi.org/10.7717/peerj.704 Wilkins, K. A., and M. C. Otto. 2003. Trends in duck breeding populations, 1955–2003. Administrative Report. U.S. Fish and Wildlife Service, Laurel, Maryland, USA. [online] URL: https:// www.fws.gov/migratorybirds/pdf/surveys-and-data/Population-status/ Trends/TrendsinDuckBreedingPopulations03.pdf Willie, M., D. Esler, W. S. Boyd, T. Bowman, J. Schamber, and J. Thompson. 2020. Annual winter site fidelity of Barrow’s Goldeneyes in the Pacific. Journal of Wildlife Management 84 (1):161-171. https://doi.org/10.1002/jwmg.21767 Wilson, S., E. M. Anderson, A. S. G. Wilson, D. F. Bertram, and P. Arcese. 2013. Citizen science reveals an extensive shift in the winter distribution of migratory Western Grebes. Plos One 8(6): e65408. https://doi.org/10.1371/journal.pone.0065408

Editor-in-Chief: Alexander L.Bond Subject Editor: Cat Horswill Erratum: In the original publication Appendix 1 was incomplete. This complete appendix was attached to the manuscript on 31 March 2021. Appendix 1 Species-specific survey windows (.) were assigned based on local knowledge of the months in the non-breeding season that each species is most prevalent off the coast of British Columbia, Canada. Species were also classified into guilds based on migration distance and dietary specialization following Bower (2009) and Billerman et al. (2020).

Survey window Guild assignment

April

March January

October Migration Dietary

February

December November Species Name September distance specialization Brant . . . Long Distance Herbivore Canada Goose . . . Local Breeder Herbivore Trumpeter Swan . . . Short Distance Herbivore Gadwall . . . Local Breeder Herbivore Eurasian Wigeon . . . Long Distance Herbivore American Wigeon . . . Local Breeder Herbivore Mallard . . . Local Breeder Herbivore Northern Pintail . . . Short Distance Herbivore Green-winged Teal . . . Short Distance Herbivore Ring-necked Duck . . . Short Distance Omnivore Scaup Spp...... Long Distance Omnivore Harlequin Duck . . . Local Breeder Benthivore Surf Scoter . . . Long Distance Benthivore White-winged Scoter . . . Short Distance Benthivore Black Scoter . . . Long Distance Benthivore Long-tailed Duck . . . Long Distance Benthivore Bufflehead . . . Short Distance Benthivore Common Goldeneye . . . Short Distance Benthivore Barrow's Goldeneye . . . Short Distance Benthivore Hooded Merganser . . . Local Breeder Piscivore Common Merganser . . . Local Breeder Piscivore Red-breasted Merganser . . . Short Distance Piscivore Horned Grebe . . . Short Distance Piscivore Red-necked Grebe . . . Short Distance Piscivore Western Grebe . . . Short Distance Piscivore Black Oystercatcher . . . Local Breeder Benthivore Black-bellied Plover . . . Long Distance Benthivore Killdeer . . . Local Breeder Omnivore Black Turnstone . . Long Distance Benthivore Surfbird . . . Long Distance Benthivore Dunlin . . . Long Distance Benthivore Greater Yellowlegs . Short Distance Benthivore Common Murre . . . Local Breeder Piscivore Pigeon Guillemot . . . Short Distance Piscivore Marbled Murrelet . . Local Breeder Piscivore Bonaparte’s Gull . . Long Distance Omnivore Heermann's Gull . Long Distance Piscivore Mew Gull . . . . Short Distance Omnivore Ring-billed Gull . Short Distance Omnivore California Gull . . . Short Distance Omnivore Appendix 1

Survey window Guild assignment

April

March January

October Migration Dietary

Feburary

December November

Species Name September distance specilization Thayer's Gull . . . Long Distance Omnivore Glaucous-winged Gull . . . Local Breeder Omnivore Red-throated Loon . . . Short Distance Piscivore Pacific Loon . . . Long Distance Piscivore Common Loon . . . Short Distance Piscivore Pelagic Cormorant . . . Local Breeder Piscivore Double-crested Cormorant . . . Local Breeder Piscivore Great Blue Heron . . . Local Breeder Omnivore Bald Eagle . . . Local Breeder Omnivore Belted Kingfisher . . . . Local Breeder Piscivore Appendix 2 Twenty-year trends of costal waterbirds residing in the Salish Sea, British Columbia, Canada. The black dots on the graph are estimated indices of annual population size as calculated by the statistical model, with error bars representing the 95% credible intervals for the annual indices. Annual indices are expressed on a linear scale and represent the average of the predicted number of individual birds detected per day of survey. The black line is a smoothed visualization of the change in annual indices over time. The title of the plot contains the estimated linear trend value expressed as annual percent change per year of mean total count. The lower and upper limits of the 95% credible interval (CI) of the trends are shown in parentheses along with the posterior probability of the trend: a value greater than or equal to 0.95 provides additional support for the observed trend. Appendix 2 Appendix 2 Appendix 2 Appendix 2 Appendix 2 Appendix 2 Appendix 3 Twenty-year trends of costal waterbirds residing in the outer costal waters of the Pacific Ocean, British Columbia, Canada. The black dots on the graph are estimated indices of annual population size as calculated by the statistical model, with error bars representing the 95% credible intervals for the annual indices. Annual indices are expressed on a linear scale and represent the average of the predicted number of individual birds detected per day of survey. The black line is a smoothed visualization of the change in annual indices over time. The title of the plot contains the estimated linear trend value expressed as annual percent change per year of mean total count. The lower and upper limits of the 95% credible interval (CI) of the trends are shown in parentheses along with the posterior probability of the trend: a value greater than or equal to 0.95 provides additional support for the observed trend. Appendix 3 Appendix 3 Appendix 3 Appendix 3 Appendix 3